imx: imx8mq-phanbell: enable CONFIG_DM_SERIAL

Marked related nodes as u-boot,dm-spl for serial driver model
Enable CONFIG_DM_SERIAL

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Fabio Estevam <festevam@denx.de>
2 files changed